As a result of manufacturing, detector modules for a detector of an x-ray computer tomograph do not always exhibit identical imaging properties, that is to say in some circumstances they supply divergent signals when the same x-ray intensity is irradiated. When a detector is constructed by using detector modules whose properties exhibit an impermissibly high spread, this can have a negative influence on the quality of an image produced thereby.
With regard to this, the quality of the detector modules is tested in accordance with the prior art. The detector modules are usually mounted on a detector device. This is a frame of generally arcuate design and having a multiplicity of juxtaposed slots for connecting the detector modules. With regard to the quality of the detector module, it is possible to tolerate spreads of different intensity in the properties, depending on the position of a detector module on the detector device.
Detector modules with a large spread in their properties are usually mounted in the vicinity of the ends of the detector device, whereas detector modules with a low spread in their properties are mounted in the middle of the detector device.
In accordance with a first method according to the prior art, the detector device for holding detector modules is fitted completely with detector modules. Subsequently, the image quality that can be achieved with the detector is tested. If the image quality does not correspond to prescribed criteria, the arrangement of the detector modules is changed using the “try and error” principle until the desired image quality has been achieved. The known method is lengthy and requires the use of specially qualified staff. Apart from this, it is not possible to predict the time period for testing the image quality, and this disturbs the production cycle. Finally, it is possible with the aid of the known method for the quality of the detector modules used to be determined only relatively and not absolutely.
In accordance with a second method, known from DE 198 11 044 C2, the imaging properties of each detector module are tested before the production of the detector by using a special test station. The measurement results obtained in this case are then used with the aid of a special selection method to allocate the detector modules installation positions on the detector device. The provision of a special test station is costly. Moreover, there is a need, in turn, for specially trained staff to operate the special test station.